tools: mkeficapsule: use %zd to print ssize_t.

For printing a ssize_t variable we must use %zd and not %ld to avoid
a -Wformat error on 32-bit systems.

Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/tools/mkeficapsule.c b/tools/mkeficapsule.c
index 49f5b78..fb6c57f 100644
--- a/tools/mkeficapsule.c
+++ b/tools/mkeficapsule.c
@@ -866,12 +866,12 @@
 
 	dtb = malloc(dtb_size);
 	if (!dtb) {
-		fprintf(stderr, "Can't allocated %ld\n", dtb_size);
+		fprintf(stderr, "Can't allocated %zd\n", dtb_size);
 		return NULL;
 	}
 
 	if (fread(dtb, dtb_size, 1, f) != 1) {
-		fprintf(stderr, "Can't read %ld bytes from %s\n",
+		fprintf(stderr, "Can't read %zd bytes from %s\n",
 			dtb_size, path);
 		free(dtb);
 		return NULL;